Adjustable live center



Oct. 9, 1962 G. J. BENES 3,057,238

ADJUSTABLE LIVE CENTER Filed Aug. 1, 1960 3O 20 /4 /2 CENTER um; 0F

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40 CLENTER U E OF EXTERNAL SLEEVE DIAMETER \6 AND ARBOR BORE 5o INVENTOR. GORDON J. BENEs BY M 7s 20 WI 7 a United States Patent Ofiice 3,57,238 Patented Oct. 9, 1962 3,657,238 ADJUSTABLE LIVE CENTER Gordon 5. Bones, Riverside, llL, assignor to lEnco Manufacturing (30., (Ihicago, Ill, a corporation of Illinois Filed Aug. l, 196%), Ser. No. 46,551 1 Claim. Cl. 82-33) This invention relates generally to centers for supporting work pieces in machines such as lathes, grinding machines, and the like, and more particularly relates to an improved work-supporting center which is both live and adjustable.

The use of centers of both the live and dead type for supporting work-pieces in machines such as lathes is of course old and well known. Similarly, there have more recently been provided various centers and related auxiliary devices which are adjustable for purposes of taper work and/ or correction of machine misalignment. While prior adjustable dead centers have proved generally satisfactory, the same cannot be said for the previously attempted adjustable live centers.

The problems attendant adjustable live centers may be attributed in part to the fact that the tips thereof must be rotatably mounted by means of ball or roller bearings or the like. As a result, the prior adjustable live centers have generally been characterized by a relatively complex and expensive structure having a number of moving parts in the adjusting means. Owing to the complex structure, they were often inherently inaccurate or readily rendered so with repeated use. Other disadvantages were the irregular configuration necessitated by the complex adjusting means, the fact that the adjusting means often bound or galled and the lack of means capable of cornpensating for the expansion of parts caused by friction during operation.

It is therefore an important object of this invention to provide an adjustable live center which is extremely accurate for holding a work piece in an exact measured center or off-center position.

Another object is to afford an adjustable live center of the character described calibrated to give direct readings of the amount of ofif-center adjustment.

A further object is to provide an adjustable live center of the character described having adjusting means which cannot gall or bind and yet are sufficiently resistant to any inadvertent movement thereof. In this regard, the device employs male and female members having precision ground tapers of critically predetermined angles.

Still another object is to afford an adjustable live center of the character described having means for compensating for the normal expansion of parts resulting from operational friction.

Yet another object is to provide an adjustable live center of the character described which is of substantially smooth and regular configuration thereby eliminating all objectionable enlarged or protruding parts.

Still a further object is to afford an adjustable live center of the character described which may likewise be utilized as a dead center.

Yet a further object is to provide an adjustable live center of the character described which may be relatively inexpensively fabricated and yet is most efiicient, simple to operate and sturdy.

With the foregoing and other objects in view which will appear as the description proceeds, the invention consists of certain novel features of construction, arrangement and a combination of parts hereinafter fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claim, it being understood that various changes in the form, proportion, size and minor details of the structure may be made without departing from the spirit or sacrificing any of the advantages of the invention.

For the purpose of facilitating an understanding of my invention, I have illustrated in the accompanying drawings a preferred embodiment thereof, from an inspection of which, when considered in connection with the following description, my invention, its mode of construction, assembly and operation, and many of its advantages should be readily understood and appreciated.

Referring to the drawings in which the same characters of reference are employed to indicate corresponding or similar parts throughout the several figures of the draw- FIG. 1 is a side elevational view of an adjustable live center embodying the principles of my invention;

FIG. 2 is a longitudinal sectional view thereof; and

FIG, 3 is an enlarged cross-sectional view taken on the plane of line 33 in FIG. 2, viewed in the direction indicated, and illustrating the adjustment path of the center tip.

Turning first to FIGS. 1 and 2 of the drawings, reference numeral 8 indicates generally an adjustable center comprising a mounting member or sleeve 10, an arbor l2 and a rotatable center 14. The sleeve 10 comprises the external portion for insertion into the tail-stock quill of a lathe, grinder or other machine. The external diameter or surface 16 thereof may be tapered longitudinally as illustrated, or the sleeve may be of uniform diameter and straight. In the embodiment illustrated, the sleeve 10 is formed with a front collar 17 which is calibrated in a manner and for purposes which will be subsequently described.

Formed in the sleeve 10 is an arbor-receiving bore 18 which opens to the front of the sleeve. The bore 18 is eccentric to the external diameter or surface 16 of the sleeve 10 and it is important to note that said bore is tapered with two precalculated tapers, a holding taper 20 and a releasing taper 22. The holding taper 20 is approximately 1 /2" from the horizontal and is so designated because it has been determined that if a cooperating male member is pushed into a female taper of this angle, the male member cannot be readily or inadvertently removed but must be forced or knocked out. The releasing taper 22 is approximately 5 from the horizontal and is so designated because it has been determined that irrespective of how much force is employed to push or knock together cooperating male and female members of this taper, the members will not bind or stick.

The arbor 12 comprises a head 24 and a stem 26. The stem 26 is tapered to precisely cooperate with the bore 18 and thus has a holding taper and a releasing taper of complementary but identical dimensions as the holding and releasing tapers 2t) and 22. As a result of this metalto-metal contact which eliminates substantially all radial movement, the center achieves a degree of accuracy heretofore unavailable in devices of this type. In actual manufacture, the tapers of the sleeve 1-0 and arbor 12 are ground after hardening and then precision lapped to each other for perfect bearing so that the space therebetween, as at 28, is on the order of .005 inch to .010 inch. The stem 26 may likewise be formed with a recessed area 29 to afford a lubricant reservoir for preventing galling of the sleeve 10 and arbor 12 during adjustment.

A bore 30 is formed in the arbor 12 and extends through the entire length thereof. Said bore 30 includes a reduced-diameter portion 32 and a further reduced-diameter internally threaded portion 34, said reduced diameter portions thereby affording annular shoulders 36 and 38 respectively, the functions of which will be subsequently disclosed. It is important also to note here that the bore 30 is eccentric with the external diameter of the stem 26,

for reasons which will become apparent as the description proceeds.

Rotatably positioned in the bore is the center 14. The center 14 may comprise any of the types commonly employed such as bull centers or female centers, but in the embodiment illustrated, the same comprises a straight bullet-like center having a tip 40. The rotatable mounting of the center 14 may be accomplished in any suitable manner such as by means of annular spindle bearing assemblies 42 and 44 as illustrated. The bearing assemblies 42 and 44 may be retained by means of annular retaining rings such as 46' and 48, and it will be seen that the shoulder 36 also cooperates for this purpose. Retaining rings such as 50 and 52 may likewise be employed to prevent the center 14 from falling out of the arbor 12. A suitable grease seal such as 54 is positioned in the bore 30 for purposes of retaining grease or other bearing lubricant and also preventing the entrance of foreign particles such as dust, dirt and chips into said bore. For purposes of the bearing lubrication described, the arbor head 24 may be formed with a grease hole 56 and a removable grease plug 58. While the grease plug 58 is illustrated as being threadedly engaged in the hole 56, the same may likewise be simply frictionally press-fitted therein.

A coil spring 60 and a thrust bearing 62 are positioned in the reduced diameter portion 32 of the bore 30, said spring 60 bearing against the shoulder 33 and adapted to normally urge the thrust bearing 62 against the center 14. It will thus be appreciated that the spring 60 and thrust bearing 62 afiord means for compensating for any expansion of the work piece or center 14 caused by heat generated in the machining operation.

The rear of the sleeeve 10 is formed with a rearwardlyopening recess 64 and a forwardly extending bore 66 which communicates with the bore 18. A retaining screw 68 is positioned throughout the bore 66 and is threadedly received by the threaded bore portion 34. Disc washers such as 70 and spring washers such as 72 are positioned as indicated, and the screw 68 is tightened to exert the proper pressure to keep the sleeve 10 and arbor 12 in perfect adjustable contact. Such a construction greatly minimizes the radial or thrust play of the arbor. The screw 68 is provided with suitable means for preventing the rotation thereof relative to the stem 26; said means comprising here a cross plug 74 of nylon or the like which is positioned through an opening formed laterally through said screw. The plug 74 is jammed into the threading as the screw is tightened to thereby provide a tight binding fit. It will thus be apparent that the frictional resistance to rotation between the screw 68 and stem 26 is much greater than between the screw 68 and sleeve 10.

To complete the assembly there may be provided a knockout cap 76 which is frictionally press-fitted into the recess 64. The purpose of the cap 76 is to prevent damage to the device in the event that a knockout bar is required to remove the same from the machine in which it is positioned.

Turning now to FIG. 3 of the drawings, the manner in which the lateral adjustment of the tip 40 is accomplished will become apparent to those skilled in the art. The external sleeve surface 16 and arbor bore 30 are eccentrio with the sleeve bore 18 and outer diameter of arbor stem 26 as indicated by the labelled center lines. In the illustration, these eccentricities exactly offset each other so that the tip 40 is at dead center. However, it will be appreciated that as the arbor 12 is rotated through an arc of 90 both clockwise and counterclockwise, the tip 40 will be caused to move laterally and describe the travel path indicated at 78.

In the embodiment illustrated, the vertical displacement between the described eccentricities is .006 inch which will of course compensate for .012 inch on either side of the diameter of the work piece. Thus, as indidated in FIG. 1 of the drawings, the collar 17 is calibrated directly in thousandths of an inch from zero to twelve on either side of dead center. The zero setting of course corresponds to the lower center line described in FIG. 3. Similarly, the head 24 of the arbor 12 is provided with a zero setting reference mark and a plus and minus marking on opposite sides thereof. It will thus be appreciated that if the operator rotates the arbor 12 away from him (towards the reference as viewed in FIG. 1) the tip 40 will be displaced laterally toward him, whereas, if the arbor is rotated toward him (toward the (-1-) reference), the tip will be laterally displaced away from him.

For purposes of accomplishing the described adjustment, the arbor head 24- is provided with a pair of rod holes as indicated in FIG. 1. The rod holes 80 are adapted to receive a bar or rod (not shown) by means of which, the adjustment may be readily made.

It should be understood, that while the invention has been described as comprising a live center, the same may likewise be employed as a dead center. For this purpose, it is simply necessary to remove the rotatably mounted center 14 and substitute therefor a tip sized to be frictionally and nonrotatably positionable in the arbor bore 30.

From the above description and drawings, it should be apparent that I have provided a new and highly improved adjustable center which may be used as a live or dead center. The adjusting means which includes the holding taper 2t and the releasing taper 22 insures an extremely accurate adjustment at all times. The coil spring 69 and thrust bearing 62 affords means to compensate for any expansion resulting from friction during operation. The retaining screw 68 and its associated assembly insures that the proper tension can be exerted at all times between the arbor and sleeve, and this feature in combination with the described tapers insures an accurate and readily made adjustment without any binding or galling. The external contour of the adjustable center is substantially straight, thereby eliminating all undersirable bulky protrusions. Further, calibrations are provided which quickly give a direct reading in practical units. In addition, the entire structure is greatly simplified over prior similar structures so that the same is more durable and may be less expensively manufactured.

It is believed that my invention, its mode of construction and assembly, and many of its advantages should be readily understood from the foregoing without further description, and it should also be manifest that while a preferred embodiment of the invention has been shown and described for illustrative purposes, the structural details are nevertheless capable of wide variation within the purview of my invention as defined in the appended claim.

What I claim and desire to secure by Letters Patent of the United States is:

An adjustable live center comprising an elongated sleeve having an arbor-receiving bore opening to the front thereof, said arbor-receiving bore being eccentric to the outer surface of said sleeve, said arbor-receiving bore being eccentric to the outer surface of said sleeve, said arborreceiving bore being formed with a holding taper of 1% from the horizontal and a releasing taper of 5 from the horizontal, an elongated arbor having a head and a rearwardly projecting stem, said stem having a pair of identical cooperating tapers 1 /2 and 5 and being positioned in said arbor-receiving bore so that said arbor is in face to face contact with a substantial portion of the entire wall of said arbor-receiving bore, said stem being formed with a threaded hole opening to the back thereof, said arbor being formed with a tip-receiving bore concentric with said outer surface of said sleeve, said tip-receiving bore including a reduced diameter rearwardly extending portion, a work-supporting tip rotatably mounted in said tipreceiving bore, a thrust bearing and a coil spring mounted in said reduced diameter portion, said coil spring normally urging said thrust bearing against the back of said tip, means for efiecting the adjustable rotation between said arbor and sleeve, a headed screw extending through the back of said sleeve and cooperating with said threaded hole, compressible jamming means associated with said screw for preventing relative rotation between said stern and said screw, resilient spring means mounted between the head of said screw and the back of said sleeve, practical measurement units calibrated on said sleeve adjacent the front edge thereof, and reference marks on said ar-bor head for cooperating with said calibrations whereby the exact amount and direction of offcenter adjustment of said tip may be directly determined.

References Cited in the file of this patent UNITED STATES PATENTS 1,962,499 Garing June 12, 1934 2,189,242 Edwin Feb. 6, 1940 2,376,905 Davenport May 29, 1945 2,392,037 Galloway Jan. 1, 1946 2,520,473 Shepard Aug. 29, 1950 6 2,531,809 Fish Nov. 28, 1950 2,547,858 Dearborn Apr. 3, 1951 2,780,467 Jackson Feb. 5, 1957 2,841,042 Jacobs July 1, 1958 2,847,890 Jacobs Aug. 19, 1958 2,860,538 Bruet Nov. 18, 1958 2,951,407 Olson Sept. 6, 1960 FOREIGN PATENTS 279,694 Switzerland Dec. 15, 1951 410,968 Great Britain May 31, 1934 721,744 Great Britain Jan. 12, 1955 915,404 Germany July 22, 1934 1,145,484 France Feb. 23, 1956 OTHER REFERENCES BrochureEncos New Micro-Set adjustable Center distributed by Enco Manufacturing Company, 4520 West Fullerton Avenue, Chicago 39, 111., at the A.S.M.E. Machine Tool Show in Philadelphia, Pa., on May 1, 1958. 1 page of content.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,057,238 October 9 1962 Gordon J. Benes error appears in the above numbered pat- It is hereby certified that t the said Letters Patent should read as ent requiring correction and the, corrected below.

lines 58 and 59, strike out "said arbor- Column 4 face of said receiving bore being eccentric to the outer sur sleeve,

Signed and sealed this 19th day of February 1963.

(SEAL) Attest:

ESTON G. JOHNSON DAV LADD i Commissioner of Patents Attesting Officer 

